The present invention relates generally to an optical substance manipulator, and more particularly to an optical substance manipulator harnessing the principles of optical tweezers, which are applied to some fields such as biochemical, molecular mechanics and micro•nanoscale thermofluid engineering fields.
Optical substance manipulation techniques represented by an optical tweezers device are capable of manipulating a microscale substance in a non-contact, non-destructive fashion. There is an optical tweezers technique extensively put into practical use, in which light is tightly focused by an objective lens or the like into a medium such as a solution or air, so that a substance (particles) can be picked up near the focus of incident light by virtue of light pressure occurring at the substance interface in the medium (see Non-Patent Publication 1).
The optical tweezers technique is capable of picking up a substance in a non-contact way, and manipulating the captured subject three-dimensionally with a micrometric order resolving power. For this reason, there has been much achieved through its use as an experimental tool that applies any desired manipulation to a subject of sub-microscopic size such as a single cell or DNA to go deep into what happens chemically and biologically (Non-Patent Publication 2). As one example, there is the result so far reported of using optical tweezers to take hold of and manipulate microscopic particles added to both terminus of a string form of a single molecule, thereby making a knot across the molecular and measuring a tension change (Non-Patent Publication 3).
The optical substance manipulation techniques used so far in the art, for the most part, make use of laser light obtained by entering parallel light in a collective lens such as an objective lens to focus that light onto one point. With this method, strong manipulation force is obtainable because the light is focused with high intensity; however, there is the scope of action narrowing down to a few micrometers for that. Further, the directionality of manipulation force resulting from light pressure is only limited to that of trapping force toward, or repulsive force off, the laser focus. For this reason, a substance of micrometer order is manipulated by a method wherein once that substance has been trapped at the focus, the whole ambient medium or the whole laser irradiation system is moved to transfer the substance. This method works very favorably for moving a single substance to any desired position; however, it renders it difficult to apply extensive manipulation, continuous manipulation, and fast manipulation to a group of massive substances scattered in the medium.
In recent years, an idea for making up for the narrowness of the range of action of the optical tweezers technique has been proposed: there are a number of laser irradiation areas formed in a medium as by locating a special diffraction grating or the like in a laser light path to split a laser beam into multiple beams, so that multiple substances can be manipulated simultaneously (Non-Patent Publication 4, and Patent Publications 1 and 2). Also, it has been reported that by locating a cylindrical lens or the like in an optical path, the laser focus is so transformed that multiple substances can be trapped linearly (Non-Patent Publication 5). With these methods, it is true that the amount of concurrently manipulatable substances can be increased; however, they are similar to the prior art in terms of light pressure being used as a substance trapping force, and so are used mainly for substance manipulation after trapping.
To enable continuous manipulation without taking hold of a substance, it is necessary to continue to apply continued force of action to a moving substance. For instance, if a subject group of substances is in a constantly flowing state, continuous manipulation is enabled even with trapping force as light pressure. In this regard, there is a continuous manipulation method proposed, using multi-point optical tweezers using a diffraction grating (Non-Patent Publications 6 and 7, and Patent Publication 1). However, the performance of action would vary largely depending on the flowing conditions for substances. In addition, this method is inefficient because the margin of substance manipulation is narrow relative to the range of substantial light irradiation.
Patent Publication 1
JP2005-502482A
Patent Publication 2
JP2005-515878A
Non-Patent Publication 1
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Non-Patent Publication 2
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